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Appendix VI.


Pp. 309-10.    Drilling Machine for Marine Boilers.

The methods of drilling large marine boilers ' in position' was
fully described at these pages, and illustrated by Plate XIII.,
where the boiler, with its axis placed horizontally, was laid in a
suitable cradle. In Figs". 944-5 are given some views of a drilling
machine built for two purposes : first, for drilling boiler shells
when the boiler axis is vertical, a method having certain
advantages over that of Plate XIII. ; and second, for drilling the
flat ends of a boiler whose axis is horizontal. The bed of the
machine, A A, is of L-shape in plan, and there are two vertical
standards to carry the drills, one of which, B, must be traversable
along the bed to a range equal to the largest boiler diameter.
The other, c, is fixed, and horizontal adjustment deputed to the
boiler table/. The advantage of one bed for the two standards
Mes in economy of driving power and attendance. The standard
B is traversed for new position by the screw G, operated either by
hand or power, the former by the cross-handle L and the latter
from the cone R The drill saddle D, carrying the drill spindle j
for drilling or tapping, is balanced by the weight M, and can be
raised or lowered by hand through the wheel N, or by power
through the shaft K, reversal being obtained by clutching opposite
bevels at T. The drill spindle is driven from cone E and shaft F,
being reversed by the hand wheel P, which turns a worm-segment
lever that puts one or other of the bevels Q in gear, and the
spindle is adjusted for depth by the hand wheel R. The feed
cones are seen at s.

The fixed standard c carries two saddles ff for the drill
spindles ee. They are driven by another countershaft through
the cone a and vertical shaft w, and the saddles are balanced by
the weights q q. The drill saddles are raised or lowered by the
screw /, which is moved by the cross-handle r-, and the feed is
obtained either automatically from the shaft # and worm gear to
each spindle, or can be worked by hand through the cross-handle
u. The boiler shell is supported on six arms kk, which are
bolted to the table / in positions that suit the boiler diameter,
and the final clamping is done by set screws on the two arms / /.